@Abigail May,
Good news you are not pregnant. Now just must take measures so this won´t happen again. Missinformation is the biggestfactor leading to teen pregnancy. Check the links Butrflynet suggested. If you have any question do not be afraid to ask, many terms can be confusing.
Bad news you have a sexual trasmmited disease. I imagine that you were tested also for aids. Do not trust men so easily, you can never know how many sexual partners that manchild had in the past. For him you were just another conquest. At least there was one girl before you, and maybe even more girls. He simply used you. Follow closely all your doctors indication. Treatment for STD even to an underage patient is free on the US. Also doctors can held professional secret. They are not obligated to tell your parents about your sexual disease.
I wouldn´t be worried about the size of your vaginal canal. You should be more worried about getting pregnant, that is really scary. Having another human being as a responsability for te rest of his life, found ways to feed him raise him educate him. That is really scary. Many of us are grown ups with long careers, experience and stable lives and we do not dare having a child. Children are not miracles, they are people. Also you should be worried about other STD´s.
The itch will disapear gradually do not rush. There are no inmediate cures. Anyone who promises inmediate health is lying or tryng to sell you something.